Introduction

The Anangu Pitjantjatjara Yankunytjatjara Lands occupy 103 000 km2 of north-west South Australia. Although the Lands have remained unaffected by any significant development (e.g. large-scale land clearing), there have been marked changes to the vegetation via a number of processes, e.g. diminished traditional burning practices and the introduction of feral herbivores and exotic plants. Despite these processes and changed climatic conditions, the Anangu Pitjantjatjara Yankunytjatjara Lands’ mountain ranges—Tomkinson, Mann, Musgrave, Everard, and Indulkana—provide refugial habitats, such as permanent rockholes, sheltered gorges, rock slabs, and high peaks for a number of rare and relic plant species.

The remoteness and inaccessibility of the ranges of the Anangu Pitjantjatjara Yankunytjatjara Lands provide challenges for their survey and management. Fortunately many Aboriginal people, known locally as Anangu, live in close proximity to the ranges and retain an intimate knowledge of their country’s flora and fauna. Anangu knowledge has provided important contributions to the conservation of the region’s biota (e.g. Robinson et al. 2003).

Plant monitoring program

In 2009 scientists worked with Anangu traditional owners and rangers to establish a five year monitoring program for rare plants in the Anangu Pitjantjatjara Yankunytjatjara Lands (Paltridge et al. 2009). The project aimed to:

conduct aerial and ground surveys to increase knowledge of the distribution and abundance of selected rare plants; and

establish long-term monitoring sites that will provide information on responses to disturbances such as fire, weed invasion, browsing by feral animals and changing climatic conditions.

The 12 target species (Table 1) selected for the project ranged from those which may be locally abundant but have very limited distributions, to more geographically widespread species thought to be facing regional extinction. Threats to some of these species are discussed below.

Table 1. List of target species surveyed.

Scientific name

Common name

Acacia ammobia

Mount Connor Wattle

Acacia oswaldii

Umbrella Wattle

Acacia tenuior

Central Ranges Wattle

Calostemma abdicatum

Everard Garland Lily

Cremnothamnus thomsonii

Cliffside Daisy

Eremophila willsii subsp. indeterminate

Musgrave Ranges Fuschia

Goodenia brunnea

Central Ranges Goodenia

Lepidosperma avium

Central Australian Rapier Sedge

Melaleuca fulgens subsp. corrugata

Wrinkled Honey Myrtle

Prostanthera nudula

Mount Ilbillee Mintbush

Santalum acuminatum

Quandong

Teucrium reidii

Showy Germander

Threats

Buffel Grass

Two of the rarest plants in the Anangu Pitjantjatjara Yankunytjatjara Lands, the Everard Garland Lily (Calostemma abdicatum) and the Showy Germander (Teucrium reidii), are threatened by the invasion of Buffel Grass (Cenchrus ciliaris) (Figure 1), which occurs on the edges of the best known stands of both species. Buffel Grass, an introduced pasture and erosion control species, has spread rapidly since its introduction to central Australia in the 1960s. Its vigorous growth allows it to outcompete native species and significantly increase fuel loads. Broad scale control of Buffel Grass in the Anangu Pitjantjatjara Yankunytjatjara Lands is not possible with currently available techniques. Management of small, isolated populations is achievable, and with regular and ongoing control efforts it should be possible for Anangu rangers to prevent any further encroachment of Buffel Grass into rare plant populations.

High fire frequency

While most plant species in the Anangu Pitjantjatjara Yankunytjatjara Lands are adapted to fire in some way, many of the rare plants and plant communities in the region are restricted to fire shadow areas that burn only limiting factor for such species. The Wrinkled Honey Myrtle (Melaleuca fulgens subsp. corrugata) is an example of a plant that may be threatened by fire. Capable of resprouting after occasional fires, local extinction of this species has been observed after a series of three fires in 30 years. It currently has a highly fragmented distribution across the Central Ranges bioregion, occurring only at one or two sites on the highest peaks of the various range systems. Its total area of occupancy is thought to be less than 5 km2.

The mechanism by which fire is causing a decline in abundance of Wrinkled Honey Myrtle is not fully understood but is thought to be associated with the impacts of fire on soils. Hills that are frequently burnt are vulnerable to losing their soil through wind and water erosion when the vegetation cover is removed. Once the quality and quantity of soil has deteriorated, habitats become more suitable for spinifex (Triodia sp.) colonisation. As spinifex becomes established, the hills are prone to more frequent fire, and species adapted to more infrequent burning can no longer persist.

A similar process may be occurring for two of the other target species surveyed—Mt Ilbillee Mintbush (Prostanthera nudula) and Central Australia Rapier Sedge (Lepidosperma avium)—which both grow in pockets of soil at the base of large rock slabs. This microhabitat is vulnerable to soil erosion when fires remove the vegetation growing on the upper slopes of the hills which would normally impede the flow of water. Increased water velocity after fire can result in soil loss at the base of the rocks. Thus the recommended management for these species is to create fire breaks in the vegetation upslope of the plant populations. A fire management plan has been produced for the ranges of the Anangu Pitjantjatjara Yankunytjatjara Lands that prescribes fuel reduction burns to be conducted in the cooler months to limit the spread and intensity of wildfires in the hot season.

Protecting Quandong trees

Of all the plants surveyed during this project, the Quandong (Santalum acuminatum) is the species that is most relevant to Anangu because of its importance for both food and artefact production. It is also the species for which local extinction is most imminent, primarily due to over-browsing by feral camels (see Figure 2). Fire also causes death of Quandong trees, and rabbits destroy seedlings. Overharvesting of Quandong trees for the punu (wood carving) industry has also contributed to reduced population sizes, however art centres now discourage use of Quandong for artefact production.

Fortunately, Anangu have an excellent knowledge of the remaining Quandong populations on the Anangu Pitjantjatjara Yankunytjatjara Lands and have been instrumental in establishing monitoring sites for this species. Localised actions recommended to protect Quandong trees include fencing off the best stands and conducting fuel reduction burns around trees. Broadscale actions to expand current populations include widespread camel culling and fire management.

Conclusion

With on-going management actions (especially weed control and prescribed burning) by Anangu Traditional Owners and rangers, the threatening processes that face many rare and threatened plants in the Anangu Pitjantjatjara Yankunytjatjara Lands can be ameliorated.

Paltridge, R., Latz., P., Pickburn, A. and Eldridge, S. (2009). Establishing a monitoring program for rare and declining plants in the Anangu Pitjantjatjara Yankunytjatjara Lands of South Australia. Department for Environment and Heritage, South Australia.